A can do 1/4 of a work in 10 days, B can do 40% of the work in 40 days and C can do 1/3 rd of the work in 13 days. If all three are working together, in how many day they can complete the total work?

Please tell me the procedure to solve the problem

Thanks

A: Since A can do 1/4 of the job in 10 days then it takes A 40 days to finish the job. A's rate of work is 1/40
B: Since B can do 2/5 of the job in 40 days then it takes B 100 days to finish the job. B's rate of work is 1/100
C:Since C can do 1/3 of the job in 13 days then it takes C 39 days to finish the job. C's rate of work is 1/39

We can add together the rtes and find a combined rate of work for A, B, and C.

1/40 + 1/100 + 1/39 = 0.025 + 0.01 + 0.025641... = .060641025641...

To find the number of days we take the reciprocal giving us about 16.5 days.